DSC study of the cure kinetics during nanocomposite formation: Epoxy/poly(oxypropylene) diamine/organically modified montmorillonite system

Abstract

ABSTRACT:The effect of an organically modified montmorillonite (OMMT) on the curing kinetics of a thermoset system based on a bisphenol A epoxy resin and a poly(oxypropylene)diamine curing agent were studied by means of differential scanning calorimetry (DSC) in isothermal and dynamic (constant heating rate) conditions. Montmorillonite and prepared composites were characterized by X-ray diffraction analysis (XRD) and simultaneous differential scanning calorimetry-thermogravimetric analysis (DSC-TGA). Analysis of DSC data indicated that the presence of the filler has a very small effect on the kinetics of cure. A kinetic model, arising from an autocatalyzed reaction mechanism, was applied to the DSC data. Fairly good agreement between experimental and modeling data was obtained.

Analysis of the cure of epoxy based layered silicate nanocomposites: Reaction kinetics and nanostructure development

“…Regarding the effect of clay content on the activation energy, the assertion of Becker et al 9 that E generally decreases as the clay concentration increases is not really supported either by the present results (see Table IV) or, in general, by other literature data, 12,16,39 where any decrease is small and not convincing. Although the modified clay acts as a catalyst for the cure reaction, seen for example in the advance of the cure in both isothermal and nonisothermal conditions (Figs.…”

“…For example, in the same DGEBA plus amine plus organically modified MMT system Ton-That et al 12 report that the T g of the cured nanocomposite with 2 wt % clay is lower, by about 48C, than that for the epoxy/diamine without clay, whereas Ivankovic et al 16 find a decrease of 28C for the 5 wt % nanocomposite but an increase of 68C for a clay content of 10 wt %. Direct comparison of these results is not helpful, though, as the former cure schedule was dynamic at rates between 2.5 and 20 K/min whereas the latter was isothermal at cure temperatures between 918C and 1018C, always higher than the T g of the cured nanocomposite.…”

“…5,[7][8][9][10][11][12][13][14][15][16] One immediate observation that can be made from these investigations is that, even when the epoxy resin and hardener system is the same, for example diglycidyl ether of bisphenol-A (DGEBA) epoxy cured with an amine, and the nanoclay is an organically modified montmorillonite (MMT), the kinetics of the curing reaction can vary significantly and can display a number of different features depending upon the conditions of the cure process. As a consequence, the nanocomposite which results may be fully or partially exfoliated, or not exfoliated at all, which has a corresponding effect on the properties of the cured nanocomposite.…”

Effect of functionalized kaolinite on the curing kinetics of cycloaliphatic epoxy/anhydride system

“…Differential scanning calorimetry (DSC) is an effective method for the determination of the curing kinetics of epoxy resin systems with organoclays Ivankovic et al, 2006;Montserrat et al, 2008;Román et al, 2007;Saad et al, 2011;Xu et al, 2003). However, previous investigations realized a number of inconsistent reaction mechanisms and conclusions for the epoxy resins modified with organoclays.…”

Non-isothermal cure and exfoliation of tri-functional epoxy-clay nanocomposites

“…The curing process, which may involve isothermal or non-isothermal (dynamic) cure schedules, or a combination or sequence of either of these, may be monitored and characterised by thermal analysis techniques, from which a number of kinetic parameters may be obtained. These parameters and other details of the cure process can be related to the nanostructure development, and hence thermal analysis is a useful tool in the study of these PLS nanocomposites [8][9][10][11][12][13][14][15][16][17][18][19][20]. Most of the studies of the cure reaction of epoxy PLS nanocomposites have concentrated on the iso -thermal or non-isothermal cure of bi-functional epoxy resin systems, typically diglycidyl ether of bisphenol-A (DGEBA); for example, only reference 13 of those cited immediately above (references 8 to 20) does not use DGEBA.…”